Connector switch for telephone systems



Patented Feb. 20, 1951 D STATES:-

CONNECTOR swrrcn FOB TELEPHONE 'sys'rEMs'q 1 Pier Bakker, Chicago,lll.,

assignor to: Automatic 1,

ElectricnLahoratories, 12:10., ichicagm; 111. a cor-,1

noratian of. Delaware Application August; 22, 1947, Serial No; 770,035;r

; Claims. (01. 11-95-18) 2 tending to a plurality of Pr-B. Xs.Speciflcallyg-v thesubscribenline III maybe of the private typeextending to the subscriber substation Aythe sub scribenline 230 mayberef the four-party typeex-I tending to, the subscriber substations B,C and tw'o others not shownythe P. B. X' -trunk Z I il mayo betoneof agroup of two extending to the zIlIq-and the P. B; X trunk 2 2-6- may'be-ona of a t group of three extending to theP; B. X2 II. Also:- theexchange terminates subscriber lines of the five-party type, not shown;

Alsorthe exchange comprises a pluralitymf finder-connector links,including the linkvconsisting; of the finder I I15 and the connectorrlID; as s its manycontrol functions. well as an associateddistributor.484;; Also-cach Another object of the invention is to:provideasubscriber lineand each P.1B. X trunk is provided in aconnector switchof-thetrunkhuntingtypep with i a lineocircuit-individualthereto;- thev line. an improved testingh-cgndnoperating circuitl fOrcircuits Ill2and222 being individually associated;.: controlling th t kh ti r ti Wi-th ithe:.subscriber lin esM I Iiuand 238,: and the t bject,1-} t invention i t m id H-BO linelcircuitst2El2rand.2l2beingindividuallyzasson, in a connector ofthecombinationtrunk huntin ciatedWith.the P. B; Xtrunks 2 I 0 and 22M. andv party line typean improvedcombination cir- I, Eachof-the subscriber substations A93, cfetci, cuitarrangement iercontrollingctiunk :lhuntingl .1- isprovided withconventional substation appara and for selectively settingthesringingcircuit'toxi. tus;,;the. ub criber substations B: and cibeingi be,employed in ringing ;the party lines. 1 provided .Withsubstationapparatus respectively;

A further object of ,theninvention is:topro.videa connector switch of.the primary-secondary mo tions,mechanismv'type,yincorporatinganr-improved register switch arrangementior'sselectively, controllingthe variousfunctions thatareperformed by the connector switch aiterythemechanisrn ha, been operatedto performaxselection;

Further features of; the invention pertain to the particular,arrangement of; the circuit; ,ele mentsof the system, whereby thelaboyeoutlined and additional operating ,features thereof are at tained.

The, invention, bothas to its organization and method of operation,together with further obk. jects and advantages thereof, will .bestbaundere stood by reference to the. following specification; taken inconnection with the accompanying, drawings, in which, Figures 1 and 2taken to}; gether illustrate the details of an automatic'telek phonesystem having, incorporated therein the, features of the presentinvention. More particularly Figs. 1 and 2 should be arrangedrespectively i left and right in end-to-end relation in order to form aunified diagram:

Referring now moreparticularly to Fi'gswl and 2 2 of the drawings, thereis illustrated an automatic telephone system comprising anexhang'eterminating a-plurality of subscriber linesi l II=,' 23.8,etc.,extendingctcsubscriber substationsyand 1:

includingrthe ringers 2 I 3, and 2 i5, respectively, connected; viathe.condensersa E 54 and 216 :bee-e tween grdundtpotential. and therespective; line it conductors C23I'1'and 0232:.of the.assoc-iatedezsubei. scriber linea23ii. Eachof,thei=-;B; Xfs 2M, 2LI,,etc:;1is:provided with conventional'P. B; Xequips ment.;.-The linecircuits I52, 2522,12I2 andzZZlc. mayabe .of; any. :conventional type;and 13116461521" tribntor I fl l-mayybeuof any suitable utypenz Prefer;erably,; each of the fingers zlllfigetcl, is of the 200-15pointfitrowgertype including ,a .first LWiDGIE set 2', I tlfiA and asecond wiper set I053; each;providedw;: with 1 three; individualwipers.

Preferably; each ;of ,1 the: connectors is identical J: to. ;the 1connector; I II), which is of the 200=pointr 1;. strowger -type'; comprising a:Strowgermechanisms 28flgr-provided lwithra firstwipersetyiincludingzthe' :1- I

the wiper carriage is driven one step in the vertical direction awayfrom its normal vertical position. Further, a set of switch springs Sl98is associated with the wiper carriage of the Strowger mechanism 285 andoperated when the wiper carriage is driven a predetermined number ofsteps in the vertical direction away from its normal vertical positionadjacent to the level in which the P. B. X trunks 2H], 220, etc., areterminated in the contact bank associated with the first and secondwiper sets carried by the wiper carriage. Further, the connector H0comprises a minor switch 293 of the 10-point type provided step awayfrom their normal rotary positions.

Finally, the connector l l0 comprises a relay group including a backbridge relay R|20,.a line relay R130, a' hold relay RMB, a test relayRl50, a ring cut-off relay Riiiil, a rotary interrupter relay R110, aring relay RISU, a control relay R240, two transfer relays R245 andR250, two control relays R255 and 3259, a P. B. X relay R265 and awiperswitch relay R270. Finally there are associated with the connectors llU,.etc., five ringinggenerators, not shown, that may be either of 3thecode ringing or of the harmonic ringing types,

to :which five ringing conductors extend; the five ringing conductorsbeing designated No. l to N0. 5,=inc1uSive, and extending from therespective five ringing generators to the minor switches incorporated inthe connectors H0, etc.

Before proceeding with the description of the extension of the variousconnections, the numbering plan in the exchange as well as the contactbank arrangement of the connectors H9, etc.,

Will'be explained. All subscriber lines and P. B. X trunks areprovidedwith a three digit directory number, the first two digits of which areutilized to select two line terminals in the Strowger mechanismof theconnector, and the third digit of which is registered in the .minorswitch of the connector to select one of the two previously" selectedline terminals as well as one of the five ringing codes to'be employedfor ringing purposes.

Specifically, with reference to the connector Ill],

a private subscriber line, such, for example, as the privatesubscriberline lll may have the directory number 111 or 116 depending upon whetheritiappears in'the contact bankof the Strowger mechanism 280 before thefirst wiper set or be-" fore the second wiper set. A four-partysubscriber line, such, for example, as the four-party subscriber line239 may have the directory numbers 601 to 604, inclusive, assignedthereto; the first digit 6 indicating that the subscriber line 230appears in the sixth level of the Strowger mechanism 285 the seconddigit 0 indicatin that the subscriber line 239 appears in the tenthrotary position of the Strowger mechanism 280, and the third digits 1 to4, inclusive, commonly indicating that the subscriber line 230 appearsbefore the first wiper set of the Strowger mechanism 280 andrespectively corresponding to the first four ringing codes utilized tosignal the respective subscriber substations B, C andtwopthers, not

4 shown, connected thereto. Also a companion four-party subscriber line,not shown, may have the directory numbers 606 to 609, inclusive,assigned thereto; the first digit 6 indicating that the subscriber linementioned appears in the sixth level of the Strowger mechanism 280; thesecond digit 0 indicatin that the subscriber line mentioned appears inthe tenth rotary position of the Strowger mechanism 285; and the thirddigits 6 to 9, inclusive, commonly indicating that I the subscriber linementioned appears before the second wiper set of the Strowger mechanism280.

and respectively corresponding to the first four rin ing codes utilizedto signal the respective four subscriber substations connected thereto.

A first five-party subscriber line, not shown, 7

may have the directory numbers 701 to 705, inclusive, assigned thereto;the first digit 7 indicating that the subscriber line mentioned appearsin the seventh level of the Strowger mechanism 285; the second digit 0indicating that the subscriber line mentioned appears in the tenthrotary position of the Strowger mechanism 289; and the third digits 1 to5, inclusive, commonly indicating that the subscriber line mentionedappears before the first wiper set of the Strowger mechanism 280 andrespectively corresponding .line mentioned appears before the secondwiper set of the Strowger mechanism 280 and respectively correspondingto the five ringing codes utilized to signal the respective fivesubscriber substations connected thereto.

The group of two P. B. X trunks, including the P. B. X trunk 2H]extending to the P. B. X 20!, may have the directory number 610 assignedthereto; the first digit 6 indicating that this P. B. Xtrunk'groupappears in the sixth level of {the Strowger mechanism 280; the seconddigit 1 indicating that the first P. B. X trunk in this ing that this P.B. X trunk group appears in the sixth level of the Strowger mechanism280; the

second digit 1 indicating that the first P. B. X trunk in this groupappears in the first rotary position of the Strowger mechanism 280; andthe third digit 5 indicating that'the P. B. X trunks in this groupappear before the first wiper set of the Strowger mechanism 289.

In the Strowger mechanism 280 the two P. B. X

trunks-extending to the P. B. X 201 respectively occupy in the sixthlevel the first and second rorotary searching operation of the Strowgermechanism 289', as explained more fully hereinafter.

Similarly, in the-Strowger mechanism 280, thes three P. 13. Xtrunksextending to theR-B. X 2IIi respectively occupy in the sixth level thefirstp second and third rotary positions; whereby the adjacent fourthrotary position is blanki'and'the grounded resistor 28? is connectedtothe controls contact as a cut-off forrotary searching opera tion' of theStrowger mechanism280, as explained more fully hereinafter.

Also in conjunction with the'connector I IIl', it

is noted that the five ringing codes are utilized on a divided ringingbasis.

For example, in 'conjunction with the five-party subscriber linemenher703, the third ringing code is projected-over the negative line wiper28I; in response tohthe directory number 704, the fourth ringingcodeisprojected over the positive line wiper 282; and

response to the directory number 705; the fifth ringing code is projecwdover the negative line wiper 28L five-party subscriber line mentioned-ab'ove,- to which the directory numbers 706 to 'ZOO-are as,-

Similarly, in conjunction with-the signed, it is noted that in responsetothe directory number Wild the first ringing code is projected" overthe negative line-wiper284; in response to the directory number 707, thesecond ringing code: is projected over the positive line wiper 285;in"

response to the directory number 708,-the third ringing code isprojected over the negative line wiper 284; in response tothe directorynumber '709, the fourth ringing code is projected over the positive linewiper 285; and in response tothedirectory number 700,'the fifth ringingcode is projected over the negative line wiper 284.

Considering now the extension of a call 'from the subscriber substationA connected to the: in-' dividual subscriber line II I to the subscribersub 5 station E connected to the four-party subscriber I line 23s, thesubscriber at the calling subscriber substation A first initiatestheca1l;'whereby the line circuit I62 individual to the subscriber line III is controlled to applyground potential to the start conductor CIQB inorder to governthe distributor I04. The distributor I04 assigns thefinder of an idle finder-connectorlink,such, for

example, as the finder I05 of the link illustrated-i whereby the finderI05 operates to find the'calling" subscriber lineIII; it being assumedthat the subscriber line "III is accessible tothe second wiper setIilEiB of the finder I05; whereupon'th'e line circuit I02 is controlledin order to release,

the distributor I04 and to mark'the subscriber line I I I as busy to theconnectors I Ill,etc., having access thereto.

At this time a loop circuit is completed from the calling subscribersubstation A via the subscriber line Iii to the line relay RIM in the,connector H9; which loop circuit includes the line conductors CIIJE andCIB'I, the contacts I22 and I24 and the upper and lower windings of theline, relay RIM; whereupon the upper and lower windings of the linerelay RISI] are energized causing it to operate. Upon operating the linerelay RI completes. at the contacts I3I, a circuit for operating thehold relay RIM. Upon operating the hold relay RI completes, at 'the 6contacts 43*, I a path: ifor applying ground poten tial to: the Icontrol conductor. C I 08 .i'thereby: to: retain: operated thefinderLIIIS. Also, at the contacts I43, the hold'relayRI ifl'completesacircuit,

y including theset of switch springs, SI95, for:

energizing the upper winding of the control relay, R240 inorder to:causethe latterrelay to operate; Further the hold relay RIM]. completes,aththe, contacts-I42; a circuit, including the contacts. 256, forenergizingthe upper winding of the con-.1 trol relay R260 in orderitocause the latter relay, to operate." At this time the connector III]has... been seizedand is in. readiness torespond tollthei" 3 first:digit dialed atwthe calling subscribersubstaltion A.

The subscriber atthe calling.subscriberrsub; i stationA then proceedstoadial the directory; number ofcthe called subscriber substation 3,which: number may be 601 as previouslynotedm, Theline relay RI30 followsthe first digit 6; and; each: time it restores. and then reoperates, itsinterrupts and then recompletes, at the contacts I3 I, the circuit formaintaining operated the hold: relay RI40; whereby the latter relay isretained. in. itsioperated position during impulsing as it is" of theslow-to-release type. Also, each timeithe: line relay RI3U restoresand'then reoperates it completes and then interrupts, at the contactsz eI32, a circuit, including the contacts I44, 251 and: 243, forenergizingthelower winding of the controlrelayRZdU, and a multiplecircuit for energizing. the vertical magnet MIN; whereby thecontrolrelay R249 is retained in its operated positiond1iring;the firstdigit, itbeing of the slow-to-release type, and the vertical magnet MI9Iis operated intermittently. Each time the vertical magnet MI9I operates,it drives the wiper carriage of the Strowger mechanism- 280 one step inthe vertical direction; and when the wiper carriage of the Strowgermechanism 280 5 is driven one step in the vertical direction awayw fromits normal vertical position, the sets of: switch springs SI95, SW6 andSIS? are operated.

More particularly, the set of switch springs SI95. 1

.is operated into disengagement, thereby to interrupt the previouslytraced circuit for energizing; the upper Winding of the control relayR2405, Accordingly, at the. conclusion of the first digit-=1 6, theWiper-carriage of the Strowger mechanism 280 occupies its sixth verticalposition selecting, the associated sixth level of contacts in theassociated contact bank; and the line relay RIM. is; retained in' itsoperated position retaining. operated the hold relay RIM]. Shortlythere-- after, the control relay R240, being of the slowto-release type,restores to interrupt, at the con-v tacts 243 a further point in thepreviously traced multiple circuit for energizing the lower" windingthereof and for operating the vertical. magnet MI9I. Also uponrestoringthe control. relay R240 prepares, at the contacts 246, amultiple circuit traced hereinafter for energizing the Winding of thetransfer relay R245 and for operating the rotary magnet MI 92.

The line relay RI 30 then follows the second digit 0 retaining operatedthe hold relay RIM as it is of the slow-to release type. Also, each,time the line relay RI 3!] restores and then 're-Q operates, itcompletes and then interrupts, at the, contacts I 32, the previously,mentioned circuit, including the contacts I44, 25'! and 2st, for en--.ergizing the winding of the transfer relay R245 and the multiplecircuit, also including the contacts 255, for operatingthe rotary magnet'Ml'92i i wherebythe transfer relay, R245 operates and} v remainsoperated during impulsing as it is of tl'ieza slow-to-rleas type," andthe rotary 'magnet' is retained in its operated position to retainoperated the hold relay R140. Shortly thereafter the transfer. relay 245restores, it being of the slow-to-operate type. Incident to operation ofthe transfer relay R245, it completed, at the contacts 248, a circuit,including the contacts I42-and l for energizing the lower winding of thetransfer relay R255; whereby the latter relay operated through its firststep, it being of the two step type, to complete, at the contacts 253, apath, including the'contacts 25l and 248, for short-circuiting the upperwinding thereof. Accordingly, at the conclusion of the second digit 0,when the transfer relay R245 restored, it interrupted, at the contacts248, the above traced path for short-circuiting the upper winding of thetransfer relay R255; whereupon a circuit, including the contacts I42 and253, was completed for energizing in series the upper and lower windingsof the transfer relay R250 in order to cause the latter relay to operatethrough its second step. When the transfer relay R250 operates throughits second step, it interrupts, at the contacts 255, a further point inthe previously traced circuit for operating'the rotary magnet MI92; andprepares, at the contacts 254, a point in a circuit traced herein-afterfor operating the magnet M293 of the minor switch 290 when the windingof the transfer relay R245 is again energized.

The line relay Rl3il follows the third digit 1, retaining operated thehold relay RIM as it is of the slow-to-release type. Also, each time theline relay RI restores and then reoperates, it completes and theninterrupts, at the contacts I32, the previously mentioned circuit,including the contacts 144, 251 and 244, for energizing the winding ofthe transfer relay R245 and the multiple circuit, also including thecontacts 254, for operating the magnet M293 of the minor switch 290;whereby the transfer relay R245 reoperates and remains operated duringimpulsing and the magnet M293 of the minor switch 295 is operated inaccordance with the third digit 1. At the conclusion of the third digit1, the wipers 295 and linerelay RISEl is retained operated retaininoperated the hold relay Rl lfl. Shortly thereafter, the transfer relayR245 restores as it is of the slow-to-release type. When the wipers 29!and 292 of the minor switch 295 are driven away from their normalpositions one step in the rotary direction, the sets of switch springsS295 and S295 are operated. More particularly, the set of switch springsS295 is operated to prepare a circuit for operating the control relayR255; which circuit may not be completed immediately while the transferrelay R245 occupies its operated position since the operated transferrelay R245 completes,

at'the contacts 249, a path for short-circuiting,

tioned circuit, including the set of switch springs S295 and theresistor 29?, is completed for energizing the winding of the controlrelay R255;.

whereupon the latter relay operates.

Also it is pointed out normal vertical position, the set of switchsprings Sl98 is operated in order to prepare a circuit tracedhereinafter for operating the P. B. X relay R265; which circuit will notbe completed in the present example; however, the circuit mentioned isprepared since the subscriber line 235 appears in the sixth level alongwith two groups of P. B. X trunks extending to the P. B. X's 251 and 2|I.

At this time the first wiper set including the wipers 281, 282 and 283of the Strowger mechanism 280 has selected the four-party subscriberline 230 to which the subscriber substations B, C,-- etc., areconnected; and the second wiper set including the wipers 284, 285 $9286,of the Strowger mechanism 280 has selected the com:

panion four-party subscriber line, not shown,

however, the four-party subscriber line 230 is effectively selectedsince the wiper switch relay R210 occupies its restored position in thepresent j Accordingly, further operation of the' example. connector H0depends upon the idle or busy condition of the called subscriber line230. First assuming that the called subscriber line 230 is busy at thistime, ground potential appears upon the control conductor C233thereofand is ap plied to the control wiper 283 of the first wiper setof the Strowger mechanism 280; thereby ;to

complete a circuit, including the contacts 2-15,

the set of switch springs S296, the contacts 263 and 245, for operatingthe test relay Rl50. Upon operating the test relay RI55 prepares, at thecontacts I53, a holding circuit for energizing the winding thereof.Shortly following the conclusion of the third digit 1, the transferrelay R245 restores effecting operation of the control relay R255 aspreviously explained. Upon operating whereupon the latter relay restoresshortly thereafter, it beingof the slow-to-release type. Upon yrestoring the control relay R265 completes, at the contacts 254, thepreviously mentioned hold; ing circuit, including the contacts l4l, l53and 246, for maintaining operated the test relay Rl50; and interrupts,at the contacts 263, the original circuit for operating the test relayRl5ll.

Further, the control relay R250 completes, at the contacts 26!, a path,including the condenser. 'I 203, the contacts I55, and the condenserI25, for connecting the busy tone conductor C299to the line conductorCW6; whereby busy tone current is, returned over the subscriberline IIIto the.

calling subscriber substation A in order to. in-j' di'cate the conditionnoted to the subscriber there-- at. The subscriber at the callingsubscriber sub-.1

station A then disconnects in order toeifect therelease of the finderHi5 and the connector H0 in a manner more fully explained hereinafter.

Now assuming that the subscriber line 230 is idle when it.is selected bythe first wiper set of the Strowger mechanism 285, battery potentialappears upon the control conductor C233 thereof, thereby to complete apath substantially identical to that previously traced for the latterrelay at this time.

thatwhen the wiper car-' riage of the Strowger mechanism 280is drivensix steps in the vertical direction away from its 9sw-short-circuitingithevwinding,aof the test :relay I I50; andcompletes, :atthe contacts 2-52, a cir- :flClllllffOI energizing theupper winding ,of the ring -:relay;RI8II. The circuit mentioned extendsfrom e f-ground potential. by way of the'contacts MI and L'I52,1thecupper winding of'thering relay R180, :the contacts 262, theset .of switch; springs S296, .E.thecontacts:215,;and'the.control wiper283 of arthefirst wipercset of the'Strowger, mechanism 11280;.tobthecontrol conductor C233 of-the Sub. ,ascriber. linei23ilzhavingbatterypotential thereon. Shortly aftertthis circuit iscompleted, the ringrrelay. Rl8flxoperates as it is of the slow-to-operirate type. .Uponoperating the ring relay .RI-iill tcompletes, at the COIllDEtClJSTl85, aholding circuit, gincludingfi'theicontacts; M2, for energizing thei-lower winding thereofpand completes, at the :--contacts I84, a path,including. the contacts I52 ,t-"and ..I 4 I, for short circuiti-ng theupper winding thereof and. a multiple path,uincluding the. con- .-ductorC I'BB; whereby ringback tone current *isweturned over the finder I05and the sub- .-.1scriber line .III to the callingSLlbSCllbEI"Sllbstation A in order to indicate to the subscriber thereatthat the called subscriber substation B is being rung at this time.

When the subscriber at the called subscriber substation B answers thecall, a, circuit substantially identical to that previously-traced iscom- =-pleted for energizing effectively the upper winding-of the ringcut-oif-relay RISE]; whereby the .-.-latter relayoperates shortlythereafter, it being v of the: slowrto-operate type. Upon operating; the

wring cut-01f relayyRLGIl completes, at the eonttactswlfifi, a holdingcircuit, including the. con- -tacts- 4-42,. for energizing the lowerwinding thereof; interrupts-at the contacts I-BI and-1'64,the-previously traced circuit for projecting ring- ,ingcurrent over thecalled subscriber-1ine 230;

. Also'the ringsrelay RI8B completes, at the "z contacts I81, a path;including the contacts iSS, for. applyingground potential to the motorstart wconductor CI33- inorder to insure operation of the ringinggenerators connected to? the ringing c conductors-No. Ito. No.1 55,inclusive. Further,

: the ring relay/TRIED completesHat the contacts I86, aconn'ection'between" the pick-up conductor "C246 and the upper winding of thecontrol relay R240; which connection also includes the con- "tacts 242andifil. 'At the beginning of the next ringing cycle of. the liveringing generators, ground potential is-applied to the pick-up conductor(224E; wherebythe upper winding of the i control relay R24!) isenergized causing'the latter relay temperate."Upon-operating'the con-'trol relayRZMl. completes, at the contacts 2 H, ;.,.aholding'circuit,includingthe contacts I42, the resistor 238, and the contacts I86 andIE7, uffor energizing the upper winding thereof," and .r-interrupts, atthe contacts 242, the original circuit for energizing the upper windingthereof. -"ZFU.T1311BI, the control relay R240 completes, at the.contacts v2135, a path, including the wiper 292 "of the minor switch299 and the engaged first contact in the associated contact bank, thecon-.

tacts 258, theupper-winding ofthe ring cut-off v,irelayRlfiahtheicontacts 'IlI,-:i6I; I82 and 2H and the line wiperi-ZB! ofthe' first wiperszt of the Strowger mechanism 230 between the ringinga-colnductor: No. Iyand. the'negative line conductor: -::C23I of. thesubscriber line 2353; "ground potenwtial being rappliedxby way oi thecontacts I13, 164, ISB'and 2T3"and the'line wiper 262 of the first Wiperset "of the Strowger mechan sm 28!! to, the positive lineconductorxCiZEEof the sub-a.

interrupts, at the contacts I I63, the previously traced path forreturning ring back tone-current cover thecallingsubscriber line III;and interrupts, at-the contacts- I69, the path for applying groundpotential to the motor start conducrtor C I-33. Also thering cut-offrelay RIB!) interrupts, atthe contacts i 61, the previously-tracedholding circuittor energizing the'upper winding of the control%relay-R24ll in orderto causerthe latter re1ay-to restore shortlythereafter; it-being "ofathe slow-to-release type. Finally, the ringcut-"off reIay- RI-GD 'completeset the contacts" I62 and 165, a-loopcircuit, including the contacts 1 I 8 2,

*I83,--the contacts 21I,"-273 and the-line -iwipers =28I', 282,015 thefirst:wiper -setof the Strowger -mechanism 280 between the lineconductors G23I and G232 of the subscriber line 23a and the-upperand-lower windings 0f the back bridge relay RI2I];

-- which loop circuit extends to the calledsubscriber fisubstationB;whereby the back bridge relay R2 I I] operates. Upon operating the backbridge relay R120 reverses atthe contacts I2I, I22, I23 and 124,the'polarity of thecalling subscriber line I I I with:'respect totheupper and lower windingsof s the line relayRIBU; which reversal ofpolarity Also the back bridge-relay RtZO' completes, at the contactsI25, a multiple "holding" circuit, including the contacts l68-and I81,for energizing the lower windings oi the ring cut-off relay RIB!) andthe ring relay'RI80. -At

.this time the loop circuit extending from the call- -*i-ng subscribersubstation A via the subscriber line III to the upper and lower windingsof the line relayRI3U is interconnected by way of the con- "densers I26and I2! to the loop circuit ext nding from the called subscribersubstation B via'the subscriber line 23!! to the upper and lowerwindings of the back bridge relay RUZEI; whereby an operative connectionis completed between the calling subscriber substation A and the calledsubscriber substation B and the two-way communication therebetween maybegin. v

At the conclusion of the establishedconnection, 'when the subscriber atthe called subscriber .back bridge relayRIZll is interrupted; wherebythe latter relay restoresto interrupt, at the, con tacts I25, themultiple holding circuits for enersi ing theloweriwindingsof the ringcut-off relay and vertical positions.

7 RI30 is interrupted; whereby the latter relay restores to interrupt,at the contacts ISI. the circuit for maintaining operated the hold relayRI40;' whereupon the latter relay restores shortly thereafter, it beingof the slow-to-release type Upon restoring the hold relay RIM]interrupts, at the contacts I42, the multiple holding circuits forenergizing the lower windings of the ring cut-01f relay R I 69 and theringing relay R I-89 relay R140 interrupts, at the contacts I43, the

path for applying ground potential to the control conductor CI08,thereby to effect the release of thefinder I05; whereupon the linecircuit I02 is controlled in order to mark the subscriber line III asidle to the connectors IIII, etc., having access thereto. Finally, thehold relay RIM! completes, at the contacts I45, a circuit, including thecontacts I89 and the set of switch springs S196 for operating therelease magnet MI 94; and

' a multiple circuit, also including the contacts 259, for operating therelease magnet M294.

' Upon operating the release magnet Ml94 releases the wiper carriage ofthe Strowger mechanism 280; whereby it is returned to its normal rotaryWhen the wiper carriag'e of the Strowger mechanism 280 is thus released,the sets of switch springs SI95. SI96 SI91 and SI98 are operated.Specifically, the set of switch springs SI96 is operated intodisengagement. thereby to interrupt the circuit for operating therelease magnet MI94. crating the release magnet M294 releases the wipers29I and 292 of the minor switch 290; whereby they are returned to theirnormal rotary positions. When the wipers noted of the minor switch 290are thus released, the sets of switch springs S295 and S296 areoperated.

Specifically the set of switch springs S295 is actuated intodisengagement, thereby to interrupt the circuit for maintaining operatedthe control relay R255; whereupon the connector I I 0 is com-,

pletly released. When the connector I I0 is thus released, groundpotential is removed from the control conductor C233 of the subscriberline 239;

whereby the line circuit 222 is controlled in order At this time theestablished connection between the'calling subscriber substation A andthe called subscriber substation B is released and all of the apparatusinvolved therein is completely released and available for further use.

In view of the foregoing description of the opera'tion'oi the connectorI II] to extend a call from "the calling subscriber substation A to thecalled subscriber substation B in response to the directory number 601,itwill be understood that it is operative in almost an identical mannerto Upon opcontacts 241 and I42 for energizing the upper winding of therotary interrupter relay RI10; whereupon the latter relay operates. Uponoperating the rotary interrupter relay BI 10 reverses, at the contacts-I1I, I12, I13 and I14, the paths for applying ground'and ringingpotentials to the line conductors C23I and C232 of the called subscriberline 230. More particularly,'in this example, ground potential isapplied by way of the contacts I12, I6I, I82 and 2II and the line wiper28I to the negative line conductor C23I of the subscriber line 230; andthe ringing conductor No. 2 is connected by way of the wiper 292 of theminor switch 290 and the engaged'second contacts in the associatedcontact bank, the contacts 268 and 245, the upper winding of the ringcut-ofi relay RI60, the contacts I15, I64, I83 and 213 and the linewiper 282 to the positive line conductor C232 of the subscriber line239. The application of ground and ringing potentials respectivel to thenegative and positive line conductors C23I and C232 of the subscriberline 230 effect operation of the ringer 2I5 at the called subscribersubstation C either on a code basis or on a harmonic basis, thereby toindicate to the subscriber at the called subscriber substation C jagai'nto mark the subscriber line 230 as idle to the connectors IIII, etc.,having access thereto.

that a call is waiting to be answered. The subsequent operation-ot theconnector H0 in .response to answering of the call at the calledsubscriber substation C is identical to that previously explained; andthe subsequent release of the connector I I0 and the finder I05 is thesame as that previously described.- In this conjunction, when the ringrelay RI restores, incident to the release of the connector III), itinterrupts, at the contacts I88, the circuit for energizing the upperwinding of the rotary interrupter relay RIIG; whereupon the latter relayrestores to effect the complete release of the connector I III.

In view of the foregoing, it will be understood that connections may berespectively extended from the calling subscriber substation A to theother two subscriber substations, not shown, connected to the subscriberline 230 by the connector III] in response to the respective directorynumbersv 603 and 604. In this conjunction, it will be appreciated thatthe third subscriber substation,

not shown, connected to the subscriber line 239, is rung from thegenerator No. 3 via the negative line conductor C23I of the subscriberline .230; and that the fourth subscriber substation, not shown,connected to the called subscriber line 230, is rung from the generatorconductor No. 4 7

via the positive line conductor C232 of the subscriber line 230.

Finally, it will be understood that respective connections may beextended from the calling subscriber substation A to the four subscriberlines connected to the companion four-party subscriber lines in responseto the respective directory numbers 606, 607, 608 and 609. In thisconjunction, it is noted that during the reception of the third digits6, 7, 8 or 9, the wiper 29I of the minor switch 296 bridges the sixthcontacts in the associated contact bank completing a circuit, includingthe contacts 218, 252, 248 and I42, for energizing the lower winding ofthe switch relay R210; whereuponthe latter relay operates. Uponoperating the wiper switch relay R218 completes, at the contacts 211, aholding circuit, including the set of switch springs SI91, forenergizing the upper winding thereof {interrupts at the contacts 2'II,213 and 215, the connections to the first wiper set, including thewipers 28I, 282 and 283, of the Strowger mechanism 280; and completes,

. 1'3 atfthe contactsr 2l2; 214 and 216;: connections-to the? secondwiper: set; including: the. wipers 2 8 4,

285 and 286, of the Strowgermechanismit'il." Accordingly; since the:wiper" switch relay R219. occopies its operatedfposition, the connectionis extendeditoi the" companion four-party subscriber line; the selectionof the ringing codes as well as the division of ringingbeing'under-thecontrol of thecminor switch 2% andcarried out in themannerpreviously explained. In thisv conjunction it is noted'that whentheconnector I II! is released, thesetofL-sWitch' springs Sili'lisvoperated to interrupt the holding circuit for energizing the upperwinding of'the wiper switch relay R210 when the. wiper "carriageof theStrowger mechanismZtB-is returned'to itsnormal verticalposition'causingr the wiper switch relay R210, to restore completing therelease of the connector'l i9. .Considering now the extension of aconnection from the'callingsubscriber substation A to the P;LB.JX Z'II,the call is initiated at'the calling subscriber substation A; wherebythe link illustrated 'rnaybe'taken' for use: The subscriber at thecalling subscriber substation A then dials the directory number 615;whereupon the connector I I6 responds tothe first digit '6 and to thesecond digit .1" inorder'to operate the Strowger mechan'isrn 289 to thecorresponding sixth level and firstirotaryposition. The thirdv digit isthen rcgisterediby' the connector IID in the minor switch'Zfiil in themanner'previousl'y explained; and at th'e conclusion'pf the third digit5,the transferrelay R235 restores as previously-pointed outin order tocompleteyin this example, at the contacts 241; a circuit for operatingthe P. B. X relay R255. Specifically; the setof switch springsSJIBWisoperated: since the wiper carriage of the Strowger mechanism '289occupies thesixth level; and the wiper29 I of the minor switch 288bridges the fifth contacts in the associated contact bank. Thecircuitfor operating the P. B. X rela R265 includes the contacts, I42and Z i-"I, the wiper 29! of' the minor switch 290 and'the engaged fifthlc'dn'tacts in the associated contact bank, and the set of switchsprings'Sl98. Also at this time the first wiper set, including thewipers28!, 282 and 2830f the Strowger mechanism 286 engage the first contactset in the associated sixth level terminating the first P. B. X trunkextending to the P. B. X 2H. Accordingly, at this timethe idle or busycondition of "the first P. B. X trunk extending to the P. B; X 2!! istested, ground or battery potentials being respectively upon the controlconductor thereof in the event of busy-or idle conditions thereof in theusual manner.

Assuming that the first P. B. Xtrunk extending to the P. BHX 2 II isbusy at this time, ground potential appearing upon the control conductorthereof is applied to the control wiper283 of the first'wiper set of theStrowger'mechanisrn 280- completing the previously traced circu'it'foroperating the test relay RI5E. In the present example, upon operatingthe-test relayRI 50 completes', at the contacts I54, a circuit,includingthe grounded controlwiper 283 of the first wiper sct oftheStrowger mechanism 28i the contacts 215,, the set of switch springsS295, the contacts 255, 2652111 'and'Iil-S, forenergizing the lowerwinding of "the rotary interrupter relay RITE; where upon the latterrelay operates. Upon operating the rotary interrupter relay Rimcompletes, at the contacts I15, a holding circuit, including thecontacts 255'and' I93, for energizing-the lower winding thereof; andinterrupts," atthe contacts 11],.1311'6 original circuit fonenergizingthe lower winding; thereof. Also" the rotary" interrupter relayRI-lllcompletes, at the contacts I15, a circuit, including-the contacts265,'foroperating the rotarymagnetMI92-and a multiple circuit, alsoincludingthe 'contacts 258, for energizing the lower winding of thecontrol relay R260; whereby the rotary magnet MIQZ is operated in orderto drive the wiper carriage of the Strowgermechanism' 23E! an'additionalstep in the rotary direc tion; and-th'e control relay R260 is retainedinits operated position notwithstanding operation of the control relayR255 in the manner pre viously explained; Also upon operating, therctarymagnet MIEIZ interrupts, at the contacts I93, the previouslytraced holding circuit for energizing the lower winding of the rotaryinterrupter relay Rl'ill, thereby to cause the latter relay to restore.Upon restoring the rotary interrupter relay RI!!! interrupts, at thecontacts I15; the abovetraced multiple circuit for operating the rotarymagnet M I92 and for energizing the lower winding of the control relayR260. Further, the rotary interrupter relay RI!!! interrupts, atthe'contacts I76, a further pcintin the holding circuit forenergizingthe lower winding thereof; and reprepares, at the contacts I",the previously traced connection between the test wiper 283 of the firstwiper set of the Strowger mechanism 280 and the lower winding of therotary interrupterrelay RI'IBi v Accordingly, at thistime the test relayR I50 tests the idle or busy condition of the second P. B. XtrunKZZoeXtending to the P. B. X'ZII whereupon the test relay RIM 'i.sreopcrat'ed in order to effect reoperation ofthe rotaryinterrupterrelayRIIil in the event the secondP. B. X trunkzzdextendinglto the P. B. X'ZII is busy; whereupon the rotaryinterrupter relay .Rl10 upon reoperating, effects reoperation of therotary magnet M192 and holding of the control relay R256; whereupon thewiper carriage of the Str'owger mechanisrnltfl is'driven an additionalstep in the rotary direction.

At this time the third and last P. B. a: trunk extendingto the P. B. X2! I is tested; whereupon the cycle above described. is repeated in theevent the last mentioned P. B. X trunk is busy; whereupon theWipercarriage of the Strowger mechanism Zliilis driven an additionalstep in the rotary direction beyond the P. B. X trunks extending to the.P. B. X 2 I1 fora purpose more fully explained hereinafter,

Reconsidering the operation of the connector 2m in theevent any one ofthe three P. B.X trunks extending to the P. B. X 2 is tested'as beingidle, the test relay RIEQ fails to operate; wherebythe control relayR258 restores shortly thereafter. Upon restoring the control relay R253cuts ofi at the contacts 2%, testing by the test relay RIEO'andcompletes, at the contacts 262, the previously traced circuit forenergizing the upper winding ofthe ring relay RIBD; whereby the selected:idle P. B. X trunk. extendingto the 'P. B. X' 2 I I is'seized and rung.In this con junction "it is noted that the seized P. B. X trunke'Xtending'ito' the PsBJX 2 H is always rung from the ringing generatorconductor No. I since the P. B. X relay RZoS cuts ofi. at the'contacts258, the ringing connection to the wiper 282 of the minor'switch'zfifl;and completes, at thecontacts 261, a direct connection to the ringinggenerator conductor No. I. This connection extendsfrorn the contacts 261of the operatedPrB.'Xu'elaY R265 by way of" the contacts 245 andtl'renceauger:

through the upper winding of the ring cut-ofl relay Rlfifl. The ringingcircuit is further completed through the contacts I11, I61, I82 and 211and the line wiper 28! of the first wiper set of the Strowger mechanism230 to the negative line conductor of the seized P. B. X trunk extendingtotheP.B.X2H.

In the present example, it may be assumed that the connector HEB causesthe Strowger mechanism 280 to select via the first wiper set the secondP. B. X trunk 220 extending to the P. B. X 2! I; whereby the ring relayR|80 operates in order to complete, at the contacts 184, the previouslytraced path for applying rou d potential via the control wiper 283 ofthe first wiper set of the Strowger mechanism 280 to the controlconductor C223 of the P. B. X trunk 220; whereupon the line circuit 212operates in order to mark the P. B. X trunk 220 as busy to the otherconnectors having access thereto. The operation of the ring cut-offrelay R160 in the connector lie when the call is answered on the secondP. B. X trunk 22!] in the P. B. X 2H is the same as that previouslydescribed;

and the ultimate release of the established con- ,nection between thecallin subscriber substation A and the calledP. B. 'X 2 is identical tothat previously explained.

Finally,-in conjunction with the operation of the connector Ill), it ispointed out that in the event all three of the P. B. X trunks in thegroup extending to the P. B. X 2!! are busy. the Strowger mechanism 280is controlled in order to drive the wiper carriage past the third andlast P. B. X trunk in the group mentioned; whereby the control wiper,283 of the first wiper set of the Strowger mechanism 280 engages thefourth contact in the associated contact bank terminating the groundedresistor 281; wherevby resistance ground potential is applied thereto.The application of resistance ground potential to the control Wiper 283of the first wiper set of the Strowger mechanism 280 again completes thecircuit for operatin the test relay R150. Upon operating the test relayR150 completes, at the contacts I54, the previously traced connectionbetween the lower winding of the rotary interrupter relay Rilil and thetest wiper '283 of the first wiper set of the Strowger mechanism 280;however, the rotary interrupter relay R110 is not reoperated at thistime as .it is of the marginal type, by virtue of the inclusion of theresistor 28? in the circuit for energizing 'the lower Winding thereof.Since the rotary interrupter relay R110 is not reoperated, furtheroperation of the rotary magnet Ml92 is arrested; whereby the wipercarriage of the Strowger mechanism 289 is not operated further in therotary direction. Shortly thereafter, the control relay'RZ'dQ restoresinterrupting, at the contacts 263, the test circuit for the test-relayRIEU; and completing, at the contacts 264, the holding circuit forretaining operated the test relay Rl; whereby busy tone current isreturned over the line conductor C186, the finder I05 and the subscriberline 111 to the calling subscriber substation A in order to indicate to.the subscriber thereat that all of the P. B. X trunks in the groupextending to the P. B. X 211 are busy at this time. The subscriber atthe calling subscriber substation A then disconnects in order to bringabout the release of the connector H0 and the finder in a mannersubstantially identical to that previously explained. Considering nowthe extension of a connection from the calling subscriber substation-Ato'the P. B. X 20!, the call is initiated at the calling subscribersubstation A; whereby the link illustrated may be taken for use. Thesubscriber at the calling subscriber substation A then dials thedirectory number 610; whereupon the connector H0 responds to the firstdigit 6 and to the second digit 1 in order to operate the Strowgermechanism 289 to the corresponding sixth level and first rotaryposition. The third digit 0 is then registered by the connector I I0in'the minor switch .299 inthe manner previously explained. During theregistration of the third digit 0 in the minor switch 290, when thewiper 29! thereof bridges the sixth contacts in the associated contactbank, the previously traced circuit for energizing the lowerwinding ofthe wiper switch relay R210 is completed; whereby the latter relayoperates to complete, at the contacts ZTLthe previously traced holdingcircuit for energizing the upper winding thereof; and to interrupt, atthe contacts 218, the original circuit for energizing the lower windinthereof. Also the wiper switch relay R210 interrupts, at the contacts21!, 213 and 215, the connections between the first wiper set of theStrowger mechanism 280 and the connector H8; and completes, at thecontacts 212, 214 and 216, the connections between the second wiper setof the Strowger mechanism 280 and the connector Ill]. At the conclusionof the third digit 0, the transfer relay R245 restores as previouslypointed out in order to complete, in this example, at the contacts 241,a circuit for operating the P. B. X-relay R265. Specifically the set ofswitch springs S198 is operated since the Wiper carriage of the Strowgermechanism 288 occupies the sixth level; and the Wiper 291 of the minorswitch 298 bridges-the tenth contacts in the associated contact bank.The circuit for operating the P. B. X relay R265 includes the contacts142 and 241, the wiper 291 of the minor switch 290 and the engaged tenthcontacts in the associated contact bank, and the set of switch springsS198. Alsoat this time, the second wiper set, includin the wipers 284,285, and 286, of the Strowger mechanism 280 engage the first contact setin the associated sixth level terminating the first P. B. X trunkextending to the P. B. X 20E. Accordingly, at this time the idle or busyconditionof the first P. B. X trunk extendin to the P. B. X 281 istested, ground or battery potentials'being respectively upon the controlconductor thereof in the event of busy or idle conditions thereofin theusual manner.

Assuming that the first P. B. X trunk extending to the P. B. X 20: isbusy at this time,'ground potential appearing upon the control conductorthereof is applied to the control wiper 286 of the second wiper set ofthe Strowger mechanism 280 completing the previously traced circuit foroperating the test relay R153. Upon operatingthe' test relay Rllleffects operation of the rotary interrupter relay R; whereby the latterrelay efiects operation of the rotary magnet MI92 and holding of thecontrol relay R266; whereby the wiper carriage of the Strowger mechanism280 is driven an additional step in the rotary direction; all in themanner previously explained. At this time the connector 1H3 operates totest the idle or busy condition of the second P; B. X trunk 2|ll in thegroup extending to the P. B. X 201.

The subsequent operation of the connector H0 is the same as thatpreviously described; whereby it is operated to seize the second P. B. Xtrunk 2l0 in the group extending to the P. B. X 281 in the event it isidle or the Strowger mechanism 280 is operated past the group of P. B. Xtrunks extending to the P. B. X 20i in the event the second and last P.B. X trunk 2H] therein is busy at this time. In the last mentionedevent, the connector I it operates in order to cause busy t'onecu'rrentto be returned to the calling subscriber substation A in the mannerpreviously explained. In the event either of the two P. B. X trunks inthe group extending to the P. B. X "231, is tested as idle by theconnector Hi], it is seized thereby in the manner previously explained.Assumin that the second P. B. X trunk 2 I I] in the group "extend ing tothe P. B. X 20l is seized by the connector lid, ringin current isprojected th'ereover and the line circuit 262 is operated in order tomark the P. B. X trunk 2!!) as busy to the other connectors havingaccess thereto. The subsequent operation of the connector H in responseto answering of the call on the P. B. X trunk 2113 at the P. B. X is thesame as that previously explained and the ultimate release of theconnector H!) is the same as previously described.

In view of the foregoing, it is apparent that there has been provided aconnector switch that is especially useful in C. A. X telephone systemsthat includes improved and simplified circuit controlling elements andfunctions.

While there has been described what is at present considered to be thepreferred embodiment of the invention, it will be understood thatvarious modifications may be made therein, and it is intended to coverin the appended claims, all such modifications as fall within the truespirit and scope of the invention.

What is claimed is:

1. In a telephone system including a calling line, an automatic switchassociated with said calling line, and a group of trunks accessible tosaid switch; said switch comprising a wiper set including a test wiper,first and second relays, means controllable over said calling line forop.- erating said wiper set to select the first trunk in said group,means controlled following operation of said wiper set to select any oneof the trunks in said group for completing a first test circuit for saidfirst relay including said test wipjensaid first relay being operatedvia said first test circuit in the event either a first potential or asecond potential is applied to said test wiper, means responsive tofailure of operation of said first relay for seizing the one of thetrunks in said group selected by said wiper set, means responsive tooperation of said first relay fOr completing a second test circuit forsaid second relay including said test wiper, said second relay being"operated via said second test circuit only in the event said firstpotential is applied to said test wiper, means responsive to operationof said second relay for operating said wiper set to select the nexttrunk in said group so that the trunks in said group may be successivelyselected by said wiper set, means responsive jointly to operation ofsaid first relay and to failure of operation of said second relay forreturning a busy signal over said calling line indicating a busycondition of all of the trunks in said group, said first potential beingapplied to said test wiper in response to operation of said wiper set toselect a busy one of the trunks in said group, and means for applyingsaid second potential to said test Wiper in response to operation ofsaid wiper set beyond the last trunk in said group. I

2. In a telephone system including a calling 18 line, an automaticswitch associated with said calling line, and a group of trunksaccessible to said switch; said switch comprising a wiper set includinga test wiper, a first relay, a second relay of the marginal type, meanscontrollable over said calling line .foroperating said wiper set toselect the first trunk in said .group, means controlled followingoperation of said wiper set to select any one of the trunks in saidgroupfor completing a first test circuit for said first relay includingsaid test wiper, said first relay being operated. via said first testcircuit in the event either a high potentialor a low potential isapplied to said test wiper, means responsive to failure of operation ofsaid first relay for seizing the one of the trunks in said groupselected by said wiper set, means responsive. to operation of said firstrelay forcompleting a second test circuit for said secondrelay includingsaid test wiper, said second relay being operated via said second testcircuit only in the event. said high potential is applied to said testwiper, means responsive to operation of said sec ond relay for operatingsaid wiper set to select the next trunk in said group so that the trunksin said group may be successively selected by said wiper set, meansresponsive jointly to operation of said first relay and to failure ofoperation of said second relay forreturning a busy signal over saidcalling line indicating a busy condition of all of the trunks in saidgroup, said high potential being applied to. said test wiper in responseto operation of said wiper set to select a busy one of the trunks insaid group, and means for applying said low potential to said test wiperin rev sponse tocoperation of said wiper set beyond the last trunk insaid group.

3. In a telephone system including a calling line, an automatic switchof the primary-secondary motions type associated with said callin line,and a group of trunks accessible to said switch; said switch comprisinga Wiper set including a test wiper, first and second relays, meanscontrollable over said calling line for imparting first primary motionand then secondary motion to said wiper set to select the first trunk insaid group, means controlled following said secondary motion of saidwiper set to select any one of the trunks in said group for completing afirst test circuit for said first relay including said test wiper, saidfirst relay being operated via said first test circuit in the eventeither a first potential or a second potential is applied to said testwiper, means responsive to failure of operation of said first relay forseizing the one of the trunks in said group selected by said wiper set,means responsive to operation of said first relay for com pleting asecond test circuit for said second relay including said test wiper,said second relay being operated via said second test circuit only inthe event said first potential is applied to said test wiper, meansresponsive to operation of said sec ond relay for imparting additionalsecondary motion to said wiper set to select the next trunk in saidgroup so that the trunks in said group may be successively selected bysaid wiper set, means responsive jointly to operation of said firstrelay and to failure of operation of said second relay for returning abusy signal over said calling line indicating a busy condition of all ofthe trunks in said group, said first potential being applied to saidtest wiper in response to operation or said wiper set to select a busyone of the trunks in said group, and means for applying said secondpotential to said test wiper in response to operation of said wiper setbeyond the last trunk in said group.

4. In a telephone system including a calling line, an automatic switchof the Strowger type associated with said calling line, and a group oftrunks accessible to said switch; said switch comprising a wiper setincluding a test wiper, first and second relays, means controllable oversaid calling line for stepping first in the vertical direction and forstepping then in the rotary direction said wiper set to select the firsttrunk in said group, means controlled following said stepping in therotary direction of said wiper set to select any one of the trunks insaid group for completing a first test circuit for said first relaincluding said test wiper, said first relay being operated via saidfirst test circuit in theevent either a first potential or a secondpotential is applied to said test wiper, means responsive to failureofoperation of said first relay for seizing the one of the trunks in saidgroup selected by saidwiper set, means responsive to operation of saidfirst relay for completing a second test circuit for said second relayincluding said test wiper, said second relay being operated via saidsecond test circuit only in the event said first potential is applied tosaid test wiper, means responsive to operation of said second relay forstepping in the'rotary direction said wiper set to select the next trunkin said group so that the trunks in said group may be successivelyselected by said wiper set, means responsive jointly to operation ofsaid first. relay and to failure of operation of said second relay forreturning a busy signal over said calling line indicating a busycondition of all or the trunks in said group, said first potential beingapplied to said test wiper in response to operation of said wiper set toselect a busy one of said trunks, and

means for applying said second potential to said test wiper in responseto operation of said Wiper set beyond the last trunk in said group.

5. In a telephone system including a calling line, an automatic switchassociated with said calling line, a group of trunks accessible'to saidswitch, and a plurality of other lines accessible to said switch; saidswitch comprising a wiper set including a test wiper, first and secondrelays, mea-ns controllable over said calling line for operating saidwiper set to select eitherthe first trunk in said group or any one ofsaid other lines, means controlled following operation or said-wiper setto select any one of the trunks in said group or any one. of said otherlines for completing a first test circuit for said first relay includingsaid test wiper, said first relay being operated via said first testcircuit in the event either a first potential or a second potential isapplied to said test wiper, means responsive to failure of operation ofsaid first relay for seizing the one of the trunks in said group or saidother line selected by said wiper set, means responsive to operation ofsaid wiper set to select the first trunk in said group for conditioningsaid second relay, means responsive jointly to operation of said firstrelay and to conditioning of said second relay for completing a secondtest circuit for said second relay including said test wiper, saidsecond relay being operated via said second test circuit in the eventsaid first potential is applied to said test wiper, means responsive tooperation of said second relay for operating said wiper set to selectthe next trunk in said group so that the trunks in said group may besuccessively selected by said wiper set, means responsivejointly tooperation of said first relay and to failure of operation of said secondrelay for returning a busy signal over said calling line indicating abusy condition of all of the trunks in said group or of said other line,said first potential being" applied to said testwiper in 20 response tooperation of said wiper set to select a busy one of the trunks in saidgroup or a busy one of said other lines, and means for applying saidsecond potential to said test wiper in response to operation of saidwiper set beyond the last trunk in said group.

6. In a telephone system including a calling line, an automatic switchassociated with said calling line, a group of trunks accessible to saidswitch, and a pluralitybf other lines accessible to said switch; saidswitch comprising a wiper set including a test wiper, first and secondand third relays, means controllable over said calling line foroperating said wiper set to select either the first trunk in said groupor any one of said other lines, means controlled followin operation ofsaid wiper set to select any one of the trunks in said group or any oneof said other lines for completing a first test circuit for said firstrelay including said test wiper, said first relay being operated viasaid first test circuit in the event either a first potential or asecond potential is applied to said test wiper, means responsive tofailure of operation of said first relay for seizing the one of thetrunks in said groups or said other line' selected b said wiper set,means controlled following operation of said wiper set to select thefirst trunk in said group for operating said third relay, meansresponsive jointly to operation of said first relay andto operation ofsaid third relay for completing a second testcircuit for said secondrelay including said test wiper, said second relay being operated viasaid second test circuit in the event said first potential is applied tosaid test wiper, means responsive to operation of said second relay foroperating said wiper set to select the next trunk in said group so thatthe trunks in said group may be successively selected by said wiper set,means responsive jointly to operation of said first relay and to failureof operation of said second relay for returning a busy signal over saidcalling line indicatin a busy condition of all of the trunks in saidgroup or of said other line, said first potential being applied to saidtest wiper in response to operation of said wiper set to select a busyone of said trunks or a busy one of said other lines, and means forapplying said second potential to said test wiper in response tooperation of said wiper set beyond the last trunk in said group.

7. In a telephone system including a calling line, an automatic switchassociated with said calling line, a group of trunks accessible to saidswitch, and a party line accessible to said switch; said switchcomprising first and second relays, means selectively controllable oversaid calling line for operating said switch to select the first trunk insaid group or said party line, means responsive to operation of saidswitch to select the first trunk in said group for operating said firstrelay, means for testing a trunk 01' said party line selected by saidswitch, means responsive jointly to operation of said first relay andtorsaid testing meansfor operating said second relay, means re sponsivejointly to operation of said first relay and to operation of said secondrelay for reoperating said switch to select the next trunk in saidgroup, means controllable over said calling line to register a ringingcircuit for said party line, means controlled by said register means forselectively controlling said second relay, and means including saidsecond relay for selectively setting the ringing circuit for said partyline.

8. In a telephone system including a group of party lines, and anautomatic switch having acr is sa swap of Par y i s; are it a prisingtwo wiper sets having respective access to two subgroups of said groupof party lines, means responsive to first and to second digitstransmitted thereto for operating said two wiper sets to select twocorresponding party lines in said two subgroups of party lines, a testeroperative to test over a selected one of said wiper sets any one of saidparty lines selected thereby, a plurality of ringing codes, a dividedringing circuit having a plurality of ringing settings, a relaycontrollable to select either one of said wiper sets, means including aregister switch responsive to a third digit transmitted thereto foreffecting a corresponding control of said relay and for selecting acorresponding one of said ringin codes and for selecting a correspondingone of said ringing circuit settings and for initiating operation ofsaid tester, and means controlled by said tester in the event the one ofsaid party lines selected by said selected one wiper set is tested asidle for projecting ringing current thereover utilizing said selectedone ringing code and said selected one ringing circuit setting.

9. In a telephone system including a calling line, an automatic switchof the primary-secondary motions type associated with said callin line,and a called line accessible to said switch; said switch comprising arelay, means responsive to seizure of said switch over said calling linefor operating said relay, means responsive to operation of said relayfor conditioning said switch for primary motion, means then controllableover said calling line for imparting primary motion to said switch,means responsive to said primary motion imparted to said switch forrestoring said relay, means responsive to restoration of said relay forconditioning said switch for secondary motion, means then controllablefor imparting secondary motion to said switch to select said calledline, means for testing the idle or busy condition of said called line,means controlled by said testing means in response to the testing asidle of said called line for reoperating said relay, a source of 22ringing current, and means responsive to reop eration of said relay forconnecting said source to said called line.

10. In a telephone system including a callin line, an automatic switchof the primary-secondary motions type associated with said calling line,and a called party line accessible to said switch; said switchcomprising a relay, means responsive to seizure of said switch over saidcalling line for operating said relay, means responsive to operation ofsaid relay for conditioning said switch for primary motion, means thencontrollable over said calling line for imparting primary motion to saidswitch, means responsive to said primary motion imparted to said switchfor restoring said relay, means responsive to restoration of said relayfor conditioning said switch for secondary motion, means thencontrollable over said calling line for imparting secondary motion tosaid switch to se lect said called party line, a plurality of ringingcodes, means then controllable over said calling line for selecting anyone of said ringing codes, means for testing the idle or busy conditionof said called party line, means controlled by said testing means inresponse to the testing as idle of said called party line forreoperating said relay, and means responsive to reoperation of saidrelay for projectin said selected one ringing code over said calledparty line.

PIER BAKKER.

REFERENCES CITED The following references are of record in the file ofthis patent:

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